Quantification of serum immunoglobulin in rainbow trout Salmo gairdneri under various environmental conditions

The concentration of serum immunoglobulin in different groups of rainbow trout Salrno gairdneri was measured by means of a single radial immuno&ffusion test.The normal IgM concentration was 3.3 mg ml-' in a group of free-living trout.Hypergamrnaglobulinaemia was found in PKDinfected fish and in fish from a trout farm with VHS and ERM, while the IgM concentration was low in sera from fish living under aquarium con&tions.Inhvidual variations were very pronounced.The purity of reference preparations and the specificity of antisera used were examined by crossed in~munoelectrophoresis.